Zeolites are heavily used commercial products as ion exchangers, catalysts, and in separations technology. Their useful pore sizes are limited to 10 Å or less. In the past decade, many metal oxides have been prepared with pore sizes in the 20-200 Å range as seen in C. T. Kresge, et al., “Ordered Mesoporous Molecular Sieves Synthesized by a Liquid Crystal Template Mechanism”, Nature, Vol. 359, 710-712 (1992) and J. S. Beck, et al., “A New Family of Mesoporous Molecular Sieves Prepared with Liquid Crystal Templates”, J. Am. Chem. Soc. Vol. 114, 10834-10843, (1992). Several very specific cases with materials exhibiting pores 13-17 Å were demonstrated by Y. Ying et al. (please see T. Sun, et al., “Synthesis of Microporous Transition Metal Oxide Molecular Sieves with Bifunctional Templating Molecules,” Angew. Chem. Int. Ed., Vol. 37, No. 5, pp. 664-667, 1998; T. Sun, et al., “Synthesis of Amorphous, Microporous Silica with Adamantanamine as a Templating Agent,” Chem. Commun., pp. 2057-2058, 2000; and M. Wong, et al., “Supramolecular-Templated Synthesis of Nanoporous Zirconia-Silica Catalysts,” Chem. Mater., Vol. 14, No. 5, pp. 1961-1973, 2002, (published on Web Apr. 3, 2002). There is thus a gap between the two where very few materials have pore sizes in the 10-20 Å range.
Almost all microporous and mesoporous materials are made in aqueous media using amine or surfactant templates. Generally, the template is removed by heating to 500-550° C.
Intense research activity in the synthesis, structural elucidation and properties of mesoporous materials has resulted from the discovery of MCM-41 type mesoporous molecular sieves, Kresge, et al. and Beck, et al., id. and Q. Huo, et al., “Organization of Organic Molecules with Inorganic Molecular Species into Nanocomposite Biphase Arrays”, Chem. Mater. Vol. 6, 1176-1191 (1994). By using surfactants with moderately long alkyl chain lengths, pores in the 20-50 Å range are routinely obtained. As noted, the most common preparative procedures involve the use of cationic or anionic surfactants and oppositely charged inorganic precursors, designated S+I− or S−I+, respectively where S represents the surfactant and I the inorganic species, Huo, et al., id. A second pathway involves the use of neutral amine surfactants (S°) or nonionic polyoxyethylene surfactants (N°) with neutral inorganic precursors (I°) through hydrogen bonding at the interface of the pairs, as seen in P. T. Tanev, et al., “Mesoporous Molecular Sieves Prepared by Ionic and Neutral Surfactant Templating”, Chem. Mater. Vol. 8, 2068-2079 (1996). Following these pioneering studies in the silica system mesoporous oxides of a large number of metals were prepared, F. Schüth, “Non-Siliceous Mesostructured and Microporous Materials”, Chem. Mater. Vol. 13, 3184-3195 (2001) and Q. Huo, et al., “Generalized Synthesis of Periodic Surfactant/Inorganic Composite Materials”, Nature, Vol. 368, 317 (1994). These oxides are generally not as thermally stable as the silica based products; collapse of the pore structure in many cases occurring at temperatures required for removal of the template. Titania and zirconia are special cases where the stability may be preserved to 550° C. by phosphate additions. The well known zeolites are more highly crystalline than the mesoporous materials but are limited in useful pore size to about 10 Å. A family of inorganic-organic hybrids with pores in the desired range was recently prepared, as noted by A. Clearfield and Z. Wang in J. Chem. Soc. Dalton Trans. 2002, pp. 2937-2947 (2002) and Z. Wang, J. Heising and A. Clearfield in J. Am. Chem. Soc. Vol. 125, pp. 10375-10383 (2003). These were zirconium phosphonates containing biphenyl groups. The phenyl rings can be sulfonated to produce very strong Bronsted acid catalysts.
Thus, it would be desirable if a way to produce supermicroporous metal oxides having pore sizes in the 10-20 Å range.